Field of the Invention
The present invention relates to a photoelectric conversion device, an image reading device, and an image forming apparatus.
Description of the Related Art
Photoelectric conversion devices which perform photoelectric conversion of incident light have been known.
As an example of photoelectric conversion devices, an image capturing device which includes a plurality of photoelectric conversion units configured to output optical signals, and a plurality of column circuits configured to be provided in association with the plurality of photoelectric conversion units and include amplification transistors is disclosed in Japanese Patent Laid-Open No. 2014-75620. The image capturing device further includes an output circuit configured to output a signal based on an optical signal. The image capturing device has a first state in which a column circuit operates and consumes current in preparation for an output period, and a second state in which an output circuit consumes current to output a signal based on an optical signal. The image capturing device further includes a current consumption circuit configured to consume current such that a difference in the current consumption between the first state and the second state is reduced. According to the technology disclosed in Japanese Patent Laid-Open No. 2014-75620, with the current consumption circuit, variations in the potential of a current supply line which is caused by switching between the first state and the second state may be suppressed, and noise contained in an optical signal may be reduced.
In the image capturing device disclosed in Japanese Patent Laid-Open No. 2014-75620, the current consumption is the same between the first state and the second state. However, the technology disclosed in Japanese Patent Laid-Open No. 2014-75620 does not consider a standby period during which the plurality of column circuits and the output circuit are in a standby state. Moreover, a difference in the current consumption between the standby period during which the output circuit and the plurality of column circuits are in the standby state and the period in the first state is not considered.
The difference in the current consumption between the standby period during which the plurality of column circuits and the output circuit are in the standby state and the period in the first state causes variations in the potential of the current supply line. The variations in the potential of the current supply line reduces the S/N ratio of an optical signal.